This invention is an improvement on co-owned U.S. Pat. No. 2,852,369 entitled "Digester Strainer".
Strainers of this type may be used in a wide variety of tanks or vessels regardless of shape (cylindrical, spherical, conical, or flat-sided) and regardless of size or internal pressure in the vessel. The purpose of the strainers is to permit the extraction of liquids or liquid-gas mixtures from the liquid-solid contents of the vessel. For example, the invention has proved particularly valuable to the pulp and paper industries, wherein strainers of this type have been widely used to withdraw process liquors from pulp digesters containing liquors, cellulosic materials and pulp fibers.
This invention constitutes an improvement on the above identified patent so as to expand the usefulness of the previously patented strainers while retaining the proven effectiveness of the "lap-joint" between adjacent strainer sections described and shown in the above-identified patent.
Modern process industries, including the pulp and paper industry, have continued to increase the size of vessels and other components used in their process systems. Frequently, there is a relationship between the amount of liquid to be extracted through the strainers and the total contents of a process vessel, so that larger vessels require more strainer capacity. Under the above patent, strainer capacity could be increased only by enlarging the size of the individual strainer sections, which was undesirable from the standpoint of installation and maintenance, or by installing additional strainers at another location inside the process vessel. The latter alternative is not possible in all cases, since there may be definite relationships between the location of the strainers and the effectiveness of the process.
The instant invention provides a unique type of mounting for strainer screens which, in addition to being reliable and effective, also provides a means for enlarging the open area of strainer screens to whatever degree may be required for a given process, while maintaining the individual sections of the strainers at a size and weight that can be handled easily for its installation, maintenance or replacement -- and at the same time, retaining the "lap-joint" feature to cover the major joints between adjacent sections.
Under the invention, the upper and lower sections of the strainers may be identical, thus reducing the number of spare parts which must be retained. The open area of the strainer screens may be increased to any desired extent by the use of additional center sections which may be mounted on the same type of supports as used for the top and bottom sections. A unique type of center mounted support hook permits the strainers in the low row to be hung easily during installation and the wedge shape design of this hook relieves the bottom support blocks from the full weight of the strainers. The support blocks also hold the upper strainer sections in place until the top support blocks can be fastened.